This file introduces the features and characteristics of the UCC3921 series negative floating hot swap power managers, including precision fault threshold, programmable average power limiting, linear current control, overcurrent limit and fault time, fault output indication signal, automatic retry mode or latched operation mode, shutdown control, undervoltage lockout, 250µs glitch filter on the SDFLTCH pin, etc.
The UCC1921, UCC2921, and UCC3921 family provides complete power management, hot swap, and fault handling capability. The IC is referenced to the negative input voltage and is powered through an external resistor connected to ground, which is essentially a current drive as opposed to the traditional voltage drive.
Key features include precision fault threshold programming for average power limiting, linear current control, overcurrent limit, and fault time. It offers automatic retry mode or latched operation modes with a 250µs glitch filter on the SDFLTCH pin. The device includes undervoltage lockout and is available in 8-pin DIL and SOIC packages.
The maximum allowable sourcing current is programmed using a voltage divider from VDD to generate a fixed voltage on the IMAX pin.
A capacitor must be connected to the CT pin to set the fault time, which must be longer than the time to charge the external load capacitance.
To reset the latched off device, the SDFLTCH pin must be toggled high for a duration greater than 1ms.